Receptor Tyrosine Kinases (RTKs) are clinically validated targets that can be blocked to enhance the efficacy of radiation therapy. However, the co-expression of multiple RTKs and other cell surface receptors limits this therapeutic approach. We have identified protein N-linked glycosylation (NLG) as a co-translational protein modification that can be targeted to reduce signaling of multiple over-expressed RTKs. NLG inhibition radiosensitizes cancer cells both in vitro and in vivo and research to optimize NLG inhibition is therefore required to advance this strategy to clinical trials. Based on our preliminry data, we hypothesize that discrete steps in the NLG biosynthetic machinery can be targeted to block RTK and cell surface receptor survival signaling and enhance radiation therapy. We have generated novel human cell models with NLG defects to address the role of glycosylation in mediating receptor signaling and sensitivity to ionizing radiation. We have also identified a pharmacologic strategy for blocking NLG in tumor cells. An additional component of these studies will evaluate NLG activity in xenograft tumor models of glioma using a bioluminescent molecular imaging platform. We plan to use these pre-clinical models to evaluate and test specific NLG enzymes as gene targets for therapeutic inhibition in combination with radiation therapy. This project will provide new insights into the contributions of NLG to cancer biology as well as provide therapeutic targets for enhancing radiation therapy in the treatment of malignant disease.